How Much House Can I Afford? The Real Formula Banks Use (2026 Guide)
By Zyncalc Expert Team Β· Reviewed Β· Last updated 2026
You've probably heard the same vague advice a dozen times: "Don't spend more than you can afford." Helpful β until you try to translate that into an actual dollar figure. The truth is that banks use a specific formula to decide how much they'll lend you, and if you know that formula, you can calculate how much house you can afford before you ever set foot in an open house.
This guide walks through the exact math lenders use in 2026, shows a real worked example, and gives you a way to plug in your own numbers in under two minutes.
The 28/36 Rule β The Formula Banks Actually Use
Nearly every mortgage lender in the U.S. still leans on the same benchmark: the 28/36 rule. It's the backbone of every serious mortgage affordability calculator 2026, and it comes down to two simple limits:
- 28% of gross monthly income β the maximum that should go to housing (principal, interest, taxes, insurance, HOA)
- 36% of gross monthly income β the maximum for all debt combined (housing plus car loans, student loans, credit card minimums)
That second number is what lenders call your debt-to-income ratio (DTI). Any house affordability calculator with debt to income ratio is really just an automated version of this test.
Why lenders use this exact split
Decades of loan performance data show that borrowers who stayed under 36% DTI defaulted at dramatically lower rates than those who stretched to 43% or higher. The 28/36 rule isn't arbitrary β it's the sweet spot where most households can absorb an unexpected repair, a slow month at work, or a medical bill without missing a mortgage payment.
A Real Worked Example β Making $70,000 a Year
Let's answer the very specific question how much house can I afford making $70000 a year with real math.
Sarah earns $70,000/year ($5,833/month gross). She has a $300/month car payment and $150/month in student loan payments β total existing debt: $450/month.
Applying the 28/36 rule
- Max housing (28%): $5,833 Γ 0.28 = $1,633/month
- Max total debt (36%): $5,833 Γ 0.36 = $2,100/month
- Available for housing after existing debt: $2,100 β $450 = $1,650/month
The binding limit is $1,633 (housing cap). Assume $300/month for property tax and insurance and roughly $1,333 is left for principal and interest.
What that translates to in home price
At a 2026 rate of 6.75% on a 30-year mortgage, a $1,333/month P&I payment supports a loan of roughly $205,000. Add a 10% down payment and Sarah can comfortably afford a home around $228,000. With 20% down, she can stretch to about $256,000 because the down payment covers a larger share of the price.
The most important insight in this article: Just because a lender approves you for a certain amount doesn't mean you should borrow that amount. Living at the ceiling of your DTI leaves zero room for a lost job, a broken furnace, or the surprise of children. Most financial planners recommend buying 15β25% below your maximum approval.
How Down Payment Size Changes Everything
Your down payment doesn't just shrink the loan β it changes three things at once: monthly payment, total interest paid, and whether you owe PMI (private mortgage insurance).
- Under 20% down: lenders add PMI of roughly 0.3β1.5% of the loan per year β often $100β300/month extra
- 20% down: PMI disappears entirely, freeing that money for principal
- 25%+ down: you may qualify for slightly better interest rates
On the same $250,000 home, jumping from 5% down to 20% down cuts the monthly payment by around $350β$400 and eliminates PMI β an easy $100,000+ in lifetime savings.
How Your Credit Score Changes Your Monthly Payment
Two people can shop for the same house with the same income and walk away with wildly different monthly payments β because of their credit score. Here's what 2026 rates look like across the major FICO tiers on a $250,000 loan for 30 years:
| Credit Score | Typical 2026 Rate | Monthly P&I | Total Interest (30yr) |
|---|---|---|---|
| 760+ | 6.25% | $1,539 | $304,000 |
| 700β759 | 6.75% | $1,622 | $334,000 |
| 660β699 | 7.25% | $1,706 | $364,000 |
| 620β659 | 8.0% | $1,834 | $410,000 |
| Below 620 | 9%+ | $2,012+ | $474,000+ |
Moving from a 680 to a 760 credit score saves about $170/month on the same loan β over $60,000 across 30 years. If you're close to a threshold, delaying your purchase 6β12 months to fix your credit is one of the highest-return uses of your time.
The Hidden Costs First-Time Buyers Miss
Every quality first time home buyer affordability calculator should force you to think past the monthly payment. Here's what tends to blindside new owners in year one:
Closing costs (2β5% of purchase price)
On a $300,000 home that's $6,000β$15,000 due at signing β separate from your down payment. Includes lender fees, title insurance, appraisal, inspection, and prepaid taxes and insurance.
Property tax and homeowners insurance
Any serious house affordability calculator with property tax and insurance bakes these in β a good rule is 1.25% of home value per year for tax + 0.35% for insurance, added to your monthly payment via escrow.
Ongoing costs after move-in
- Maintenance: budget roughly 1% of home value per year ($3,000 on a $300,000 home) β even if nothing breaks this year, save it for the year the roof does
- Utilities: often 50β100% higher than a similar-size apartment (more square footage, no shared walls)
- HOA fees: $200β$500/month in many condo and planned communities
- Furniture and setup: $3,000β$10,000 in the first year is normal
Run Your Own Numbers
Every combination of income, debt, down payment, credit score, and location produces a different how much house can I afford based on salary answer. Rather than doing this math on scratch paper, plug your actual numbers into our free House Affordability Calculator β it applies the 28/36 rule, factors in property tax and insurance, and shows your maximum home price and comfortable DTI range instantly.
Plug in your income, debts, and down payment to see your true maximum home price using the 28/36 rule.
Frequently Asked Questions
How much house can I afford on a $70,000 salary?+
With modest existing debts (around $450/month) and a 10% down payment at 2026 rates near 6.75%, someone earning $70,000 can comfortably afford a home around $225,000β$260,000. Larger down payments or lower existing debt push that ceiling higher.
What is the 28/36 rule for home buying?+
The 28/36 rule says monthly housing costs (principal, interest, taxes, insurance, HOA) shouldn't exceed 28% of gross monthly income, and total monthly debt shouldn't exceed 36%. It's the same standard nearly every U.S. mortgage lender uses to approve loans.
How much do I need for a down payment on a house?+
20% down is the traditional benchmark and it eliminates PMI. FHA loans allow as little as 3.5% down, conventional loans as little as 3%. Every 5% you add reduces your monthly payment noticeably and cuts total interest by tens of thousands over the loan.
Does my credit score really change my mortgage rate?+
Yes β dramatically. In 2026, moving from a 680 to a 760 credit score can drop your rate by 0.5β1.0 percentage points, saving roughly $170/month on a $250,000 loan and over $60,000 across 30 years.
What monthly costs do first-time buyers usually forget?+
The big ones are property tax and homeowners insurance (added to your monthly escrow), PMI if you put less than 20% down, HOA fees on condos and planned communities, maintenance (budget 1% of home value per year), and higher utility bills than an apartment.
Should I buy the most expensive house my lender approves?+
No. Lender pre-approvals represent the ceiling of your DTI, not the amount that leaves you financial breathing room. Most financial planners recommend buying 15β25% below your maximum approved amount so you can absorb a job loss, repair, or family change without stress.
Disclaimer: This article is for informational purposes only and does not constitute financial advice. Consult a qualified mortgage professional for personalized guidance.